He loosens up on appearances on '30 Rock' and 'Saturday Night Live.' And it hasn't hurt him in the ratings.

When the writers of "30 Rock" sent Brian Williams lines earlier this fall for his latest cameo, the NBC News anchor had a couple of suggestions. A scene in which he auditioned to be on the show's fictional comedy sketch series was "too blue" for his taste. In another, in which he approached Tina Fey's Liz Lemon about trying out for the program, Williams adopted an alter ego that paid homage to his late uncle Tony Mortarulo.

"I'm not saying I want to audition, but Nicky Mortarulo from Scotch Plains, N.J., might be interested," Williams said with a broad grin and his best Jersey inflection. "Hey, fuggedaboutit!"

Fiddling with comedic material is not traditionally the terrain of network news anchors. But Williams, who privately cuts up colleagues with his wry humor, has grown increasingly confident about showing that side of his persona.

"In airline pilot terms, I feel like I have enough stripes on my sleeve to be able to do more of it," he said in an interview last week in his corner office at the real 30 Rockefeller Plaza. "People are much savvier now. They get the difference. They know when you change hats."

Williams' growing comfort with that title comes as he approaches his fifth anniversary as anchor of "NBC Nightly News," which has cemented its rank as the most-watched evening newscast during his tenure. More remarkably, at a time when ABC's "World News" and " CBS Evening News" have continued to shed viewers, "Nightly News" has gone the other direction: After two straight seasons of ratings gains, the newscast is up again this season, averaging 8.5 million viewers, a 3% boost over the same period last year.

For that, NBC executives credit Williams' sober yet accessible approach, along with the strength of the news division's reporting corps, which includes the likes of chief foreign correspondent Richard Engel and chief White House correspondent Chuck Todd.

"People see Brian now as a destination," said executive producer Bob Epstein. "That flies in the face of everything that's been reported about the demise of network television."

"It gives people a better sense of who he is and what makes him tick," said NBC News President Steve Capus. "I've known Brian 23 years now, and there's always been that sense of humor, but it's never been out there, because he's always thought he needed the right forum to do it. He's always very cautious in making the decision to do '30 Rock' or 'SNL' or something like that, because he doesn't ever want to undermine his day job."

Williams' forays into comedy represent a sharp departure from how his predecessors conducted themselves, noted Lawrence Grossman, a former president of NBC News and PBS.

"It was frowned upon for the news anchors -- who are supposed to pull the country together in times of crisis -- to be to flip," Grossman said. "I think we tolerate a lot more of that now than back in the day when network news was the holy grail. But it still requires some discipline and some boundary lines."

Stewart, host of Comedy Central's "The Daily Show," joked that he was "really annoyed" to discover Williams' quick wit when he first invited him on in 2003.

"Nobody likes a guy who can do a real job and your job," said Stewart, calling the notion that news anchors shouldn't show a sense of humor "a false ideal."

Williams' levity may surprise viewers who see him as the consummate newsman. He's made six trips to the war zones in Afghanistan and Iraq and received numerous awards for his on-the-ground coverage of Hurricane Katrina in 2005. (This week, he received the Walter Cronkite Award for Excellence in Journalism from Arizona State University.)

"People used to always joke that Brian was born in a suit, born to do this job," said Epstein, who has known the anchor since they both worked in local television 20 years ago.

Williams speaks about the evening news with reverence, saying that when he inherited the broadcast from Tom Brokaw in 2004, he felt like Dustin Hoffman in "The Graduate."

"Everyone was saying, 'You ready for this? You think you're going to be all right?' " he recalled. "When it's the only job you've ever dreamed of having, it's impossible to relate how that felt. I still will catch my name on the door or on a piece of artwork or stationery, and I wonder when the FBI is going to come in and say, 'Are you Brian Williams?' "